A class of advanced antenna techniques to improve spectral efficiency and thereby boost overall system capacity is generally referred to as Multiple Input Multiple Output (MIMO). The MIMO technique uses a commonly known notation (M×N) to represent MIMO configuration in terms of a number (M) of transmit antennas and a number (N) of receive antennas.
It is well known that multiple transmit and receive antennas can significantly increase the data carrying capacity of wireless systems. However, for such MIMO systems, an optimal Maximum-Likelihood or Maximum A posteriori Probability (ML/MAP) detection using exhaustive search is impossible to implement. This is because a MIMO detector's complexity increases exponentially with the number of transmit antennas or/and the number of bits per constellation point.
Several suboptimal detector structures have been proposed in literature for reducing the complexity of the MIMO detector. These can be classified into linear and nonlinear detectors. Linear detectors include zero-forcing and minimum mean-square error detectors, and the nonlinear receivers include decision feedback, nulling-cancelling and variants relying on serial or successive interference cancellation. These suboptimal detectors can be relatively easy to implement but their bit-error-rate performance and/or frame-error-rate performance is significantly inferior to that of an optimum MIMO detector.
In general, most of these sub-optimal detection techniques for cancelling multi antenna interference are proposed with/without channel coding and without utilizing the potential of Cyclic Redundancy Check (CRC). In a practical system such as 5G New Radio (NR), 3rd Generation Partnership Protocol (3GPP) Long Term Evolution (LTE)/LTE-Advanced, High-Speed-Downlink-Packet-Access (HSDPA), etc. CRC bits are appended before a channel encoder at the transmitter and an error check is performed after a channel decoder of a receiver to determine whether a packet, e.g., a transport block or portion thereof, is received correctly or not.